Abstract We investigate the temporal behaviour of completion time estimates derived from scheduling algorithms that are based on the set of already known and accepted orders (static job shop problem). In a dynamic job shop environment, these estimates change over time, typically increasing. This leads to a systematic error in the completion time estimation based on static job shop algorithms. We propose an approach for calculating this systematic error. Furthermore, a method for compensating this error is derived. For some simple examples, the theory is worked out and compared with simulation results. In all cases, the estimates based on the static algorithm can substantially be improved.